1. Field of the Invention
This invention relates to coated multi-denier mixed woven textile fabrics for use in inflatable vehicle occupant restraint systems and, more particularly, to coated textile fabrics woven with fibers and yarns of different materials and denier sizes in either or both of the warp and fill directions to provide air bags and side curtains with improved physical characteristics.
2. Description of the Related Art
Current restraint systems for automotive vehicles include driver and passenger side air bags that are instantaneously gas-inflated by means such as by explosion of a pyrotechnic material at the time of a collision to provide a protective barrier between vehicle occupants and the vehicle structure. Much of the impact of a collision is absorbed by the air bag, thus preventing or lessening the possibility of serious bodily injury to occupants of the vehicle. Such air bags are located, typically, in a collapsed, folded condition housed in the steering wheel, to protect the driver, and in the dashboard, to protect a passenger seated next to the driver. Recently, the automotive industry also has introduced air bags that are stored in the back of the front seats or in the rear seats to protect the cabin occupants in the event of a collision occurring on either side of the vehicle.
More recently still, a further safety feature that is made available for passenger vehicles, especially the so-called sport utility vehicles or SUVs, are side-impact protective inflatable side curtains designed to provide a cushioning effect in the event of side collisions or rollover accidents. These side curtains are stored in the roof of the vehicle and, in the event of a collision, deploy along the interior side walls of the SUV""s cabin.
Each of these different types of air bags has different design and physical property requirements, such as gas (air) holding permeability, air pressure and volume, puncture resistance and adhesion of the coating material to a woven substrate. For example, driver side air bags must have little or no permeability and, as a result, are often made from a material having very little or no permeability. Passenger side air bags, on the other hand, require a controlled permeability, and are most often made from materials having some degree of permeability. Furthermore, all such vehicle air restraint devices must have superior packageability and anti-blocking qualities. Packageability refers to the ability for a relatively large device to be packaged in a relatively small space. Anti-blocking refers to the ability of the device to deploy almost instantaneously without any resistance caused by the material sticking to itself.
The air holding capability of side curtains is critical since they must remain inflated for an extended period of time to protect passengers in multiple rollovers. Unlike air bags which are designed to inflate instantaneously, and to deflate almost immediately after inflation in order to avoid injury to the driver and front seat passenger, air curtains used in SUVs, or in ordinary passenger vehicles, must be capable of remaining inflated in the range of from about three (3) to about twelve (12) seconds, depending upon the size of the curtain and the type of vehicle. An average passenger vehicle would require a side curtain of from about 60 inches to about 120 inches in length as measured along the length of the vehicle, and a larger vehicle, such as a minivan, would require an even longer side curtain. The maximum inflation period of a side curtain should be sufficient to protect the cabin occupants during three (3) rollovers, the maximum usually experienced in such incidents.
When such air bags are deployed, depending upon their specific location or application, they may be subjected to pressures within a relatively broad range. For example, air bag deployment pressures are generally in the range of from about 50 kilopascals (kpa) to about 450 kpa, which corresponds generally to a range of from about 7.4 (pounds per square inch) psi to about 66.2 psi. Accordingly, there is a need for fabric products and air bags which can be made to be relatively impermeable to fluids under such anticipated pressures while being relatively light in weight.
One means of improving air holding capability in vehicle restraint systems has been through coatings such as chloroprene and silicone rubber coatings, applied to the textile substrate. Wherever coated fabrics are used there exists the problem of insufficiency of adhesion of the coating to the fabric substrate. More particularly, the smoother the substrate surface, generally the more difficult it is to obtain strong adhesion of the coating material to the substrate. Furthermore, with some coatings such as silicone rubber, radio frequency (RF) heat sealing techniques cannot be used to form the bag. Thus in such instances bags are usually made by stitching, a process which requires the addition of an adhesive sealant in the stitched areas.
There have recently been developed improved polyurethane, acrylic, polyamide and silicone coatings that are coated in layers on the fabric substrates. It has been found that adhesion characteristics are greatly improved with such layered coatings. Examples of such coated fabrics and methods of coating such fabrics are disclosed in commonly assigned application Ser. Nos. 09/327,243, 09/327,244 and 09/327,245, filed Jun. 7, 1999, the disclosures of which are incorporated herein by reference and made a part of this disclosure.
In general, yarn sizes are measured by a well known weight indicator referred to as xe2x80x9cdenierxe2x80x9d and identified as units xe2x80x9cDxe2x80x9d. The greater the denier (D), the thicker and heavier is one unit of length of the yarn. The most common denier yarns presently used in such air holding devices are 420D nylon, in a 46xc3x9746 or 49xc3x9749 count weave, for driver side air bags, and 630D nylon, in a 41xc3x9741 count weave, for passenger side air bags. However, deniers as low as 210D, in a 72xc3x9772 count weave, have been used where the air bag must be housed in a tight fit, and, to a lesser extent, a 315D yarn, in a 60xc3x9760 count weave.
U.S. Pat. No. 5,704,402 discloses an uncoated air bag fabric in which weave constructions are stated to provide air bags with air permeability which does not increase by more than about fifty percent from the untensioned state when the fabric is subjected to tensile forces. These textile fabrics are stated to include yarns of different deniers within the weaves. Air bags of this type are typically used as passenger side air bags and are unsuitable for use in driver side air bags or side curtains, which must have little or no air permeability.
U.S. Pat. No. 5,863,644 discloses woven or laid structures using hybrid yarns comprising reinforcing filaments and lower melting matrix filaments composed of thermoplastic polymers to form textile sheet materials of adjustable gas and/or liquid permeability. During the formation of textile fabrics in accordance with the disclosure, polyester fibers in the weaves are melted by the application of heat to form textile sheet materials which are stated to have predetermined gas and/or liquid permeability.
U.S. Pat. No. 5,881,776 relates to a rapier woven low permeability air bag fabric and an air bag for use in a motor vehicle. The fabric is of plain weave construction and has an air permeability of less than approximately 5.0 CFM. The air bag is comprised of a plurality of panels connected together about their respective peripheries.
While these known fabrics represent somewhat successful attempts to control permeability through the incorporation of one or more features, none of these attempts have adequately solved the problem of providing a fabric of adequate impermeability whereby controlled permeability may be incorporated, where required. The present invention relates to a mixed woven coated textile fabric having yarns of different denier sizes woven for use in such inflatable air bag or side curtain restraint systems which not only provides improved adhesion of the coating to the textile substrate, but more effectively limits permeability and provides enhanced physical properties of the woven substrate, yet leaving available controlled permeability through the use of selectively sized venting apertures or other means.
It has been found that by weaving yarns of different deniers, as for example, a low denier yarn with a higher denier yarn of the same or different continuous filamentary or fibrous materials in either or both of the warp or fill directions, coating adhesion and other physical properties of the woven textile fabric are greatly improved. In particular, if for example, nylon yarns of different deniers are interwoven, the difference in deniers creates an uneven, or relatively rough surface to which polymer coatings will adhere more securely than if the surface were smooth. Further, if nylon yarns of one denier are interwoven with, for example, yarns of a different denier and different fiber material, such as aramid fiber, the woven textile fabric would not only have greater adhesion capability for coatings, but would also have increased puncture resistance properties. In addition, the use of low denier yarns woven with high denier yarns greatly improves the packageability of the air bag or side curtain for storage, while reducing the weight of the bag. Broadly stated, fabrics for such air bags generally can weigh from about 4.0 ounces per square yard (osy) to about 10.0 ounces per square yard (osy). In actual use, however, on the average, fabrics for such air bags generally weigh from about 5 to about 6 ounces per square yard. It has now been found that by combining different size and types of yarns in a single fabric weave, the strength and weight of the resultant fabric can be selectively controlled. For example, yarns of a given denier can be utilized in the warp with yarns of a lesser denier in the fill direction. Also, the warp yarns can be comprised of yarns of different deniers in an alternating regular or random fashion and the fill yarns can be comprised of yarns of the same denier or of varying or alternating deniers. Moreover, individual yarns can be comprised of continuous filaments of varying sizes blended together, or blended with other natural or synthetic fibers to control strength and weight factors inherent in the final fabric product. As will be seen hereinbelow, such combinations provide not only strength and weight benefits, but also surface adhesion properties for coating the fabrics to render them substantially impermeable to fluid pressure.
A coated woven textile fabric is disclosed, which comprises synthetic yarns of more than one denier, and a polymeric coating on at least one side thereof, the yarns and the polymeric coating being preselected respectively in deniers and thickness so as to render the fabric substantially impermeable to fluid under pressure. According to one preferred embodiment the fabric is comprised of warp yarns of about 315D nylon and fill yarns of about 210D nylon. According to another embodiment the fabric is comprised of warp yarns of about 420D nylon and fill yarns of about 315D nylon. According to yet another embodiment the fabric is comprised of warp yarns of from about 315D to about 420D nylon and fill yarns of from about 195D to about 380D aramid.
An embodiment of the invention is disclosed wherein the fabric is comprised of warp yarns of more than one denier and fill yarns of more than one denier. This fabric may be comprised of warp yarns of from about 210D to about 315D nylon and fill yarns of about 210D nylon, and the yarns are selected from the group consisting of nylon, polyester, aramid and graphite and combinations thereof.
The coating on at least one side of the fabric is preferably a thin polyurethane layer, but may also be comprised of polysiloxane, polyamide or acrylic type polymers. The same or an alternative coating may be provided on the other side of the fabric. It has been found that the coated fabric according to the invention provides excellent fluid impermeability while retaining packageability and anti-blocking qualities.
A flexible lightweight air bag for receiving and containing fluid under pressure for use in a vehicle air restraint system is also disclosed, which comprises a textile fabric according to the invention which is woven of synthetic yarns of more than one denier, and has a polymeric coating on at least one side of the fabric. The yarns and the polymeric coating are preselected respectively in deniers and thickness so as to render the air bag capable of receiving and retaining fluid under pressure in a vehicle air restraint system. The polymeric coated fabric is substantially impermeable to the fluid.
The coating on at least one side of the fabric is preferably a thin polyurethane layer, but may also be comprised of polysiloxane, polyamide or acrylic type polymers. The same or an alternative coating may be provided on the other side of the fabric forming the air bag. It has been found that the fabric according to the invention provides excellent fluid impermeability while retaining packageability and anti-blocking qualities.